Electric commutator or the like having brushes consisting of conductive liquid jets



Oct. 17, 1933- J G P, HARTMANN 1,930,933

. ELECTRIC COMMUTATOR OR THE LIKE HAVING BRUSHES CON-SISTING 0F CON'DUCTIVE LIQUID JETS Filed May 5, 1933 r, -.-1-,9s0, 93s ELECTRIC, commute, on THE. LIKE.

HAVING-YBRUSHES CONSISTINGOFICON- i DUCTIVE LIQUID JETS Julius Frederik Georg Poul Hartmann, I

Copenhagen, Denmark Application May a, 1933, Serial No. seaoe'; and

i in Germany May ,21,"1932 This invention relates to magma commu tator with movable segments and with brushes constituted by conductive liquid jets, for instance mercury jets. 1

- It is known that inrotating commutatorsfor electric machines the use of conductive liquid jets as brushes makes it possible amongst other things toiobtain' a very substantial increase of the maximum permissible voltage between com-;

9 mutator segments. However, here the formation of, sparks gives rise to difiiculties in a; similar manner, as in many other types of commutators. The invention now has for its object to eliminate objectionable effects "of the commutation arcs J5 which according to the invention isattained by I theprovision of, one or more knives of conducting material followingthe movement of the segments and insulated therefrom, which yknives serve to cut the brush jets in such a manner that ,20 the commutation arcs are formed mainly between liquid surfaces only. If the knives are vmade from a material having a high melting point, such as tungstemtheyare not at all injured by the sparks or arcs, i. e. the commutator is practically not worn, and thus the commute,

tion arcs maybe disregarded;

A further feature of the invention consists, that adjacent ends of the segments are mutually displaced in the direction of movement of thejetparticles, and that the knife is positioned in" advance of or: in the space thus formed between such adjacent ends of consecutive. segments, the

knife being preferably adjustable.-

5 vention, each brush is made upfrom two electrically connected conductive liquid 'jets which are mutually displaced both in the direction of 1 movement of the segments andflin a direction the knife.

The' invention may be applied not only to iotating electric 'conunutators of general types and Figure 1 is an end-view of one embodiment,

"perpendicular thereto, whereas the knife"which- 40 is preferably'a'djustable is so arranged as ,to'cut that jet only which is; passed 'as-the last one by I "Figure 2 shows a longitudinal s ction through the same, 7 I a Figure, 3 shows a detail of the same on a lar er scale,-

FiguresAand 5' is an felevation and an end, 6 'view'respectivelyiof part of the second embodi-- ment, and Figure 6' is a diagram illustrating the setting oftheknife.*

The direction of rotation of the segmentsand 5 the'knives which move vsynchroneously is indi--' cated by arrOws.

The 'commutator shown in Figures lj and comprises a circular row of commutator segments E1, E2, E3'E6 which co-act with two approximately straight conductive liquid jets J land J2 issuing from stationary nozzles N1 andNz respectivelyvand serving as brushes. Adjacent ends 'of' the neighboring segments are, as shown, mutually displaced in the direction of movement of the jet particles, i. e. radially, and the outer-- most end furthermore slightly overlaps the adjacent innermost' end, I 1 In or immediately in'advance of the space thus -formed a conductive ,knife is arranged.

These knives-are designated by W1, W2, Wa-Ws respectively;'as above, mentioned they move along togetheriwith' the segments,'but they are electrically insulated from the, latter. The

knives :are preferably made of tungsten or a- 5,

similar refractory material, and each knife is welded-.ontoafshank H-of steel which is rigidly M secured to accircular disc K of insulating ma- According torstill, another feature ofthe interial mounted onthe shaft D of the-commutater. I'Each segment; has a lateral flap A which 9 'byzta screw, B istrigidly secured to a seconddisc C of insulating material. The two. insulating discs are spaced by a ring M, and both'of them. are clamped in position on the shaft D between a clamping nut L and a head P on'one end erythe shaft. The 'knives preferably, are adjustable "circumferentially in order. that the time during which consecutive segments re-' main-short circuitedby the jet .may be regulated.

For this purpose the knife carrying disc K after individually by being turned around the longitudinal axis of the knifewhich is easily understoodffrom Figure) I} 1 By the cutting of the brush jet both of the commutation arcs which in the very first moment are formed between the edges a and b 110.

vided with two diametrically oppositely arranged brush devices one of which is shown only, as Figures 4 and 5 illustrate one half of the commutator only. This brush device consists of two,

preferably adjustable, nozzles N1 and N1 which are mutually displaced both in the direction of movement of the segments and in the direction of the commutator axis. From each of these nozzles a conductive liquid jet J1 and J1 respectively issues. The jets are electrically connected with each other and thus they form together a bow-like brush. In the position of the commutator shown in Figures 4 and -5 the segments E1 and'E: are shortcircuited by the jets. The short-circuiting lasts until the jet Jr is cut by the knife W1 which -is arranged axially and outside the segments and rotates with the latter. The duration of the short-circuiting thus may be varied by adjusting this knife. Furthermore inFigures-A and 5 the knives W1, W2 and the segments are mounted on the shaft D by means quite similar to those shown in Figures 1 and 2, alike details being designated by the same reference characters. Thus the knives may also here be adjusted circumferentially by relative turning of the discs K and C.

In order to completely attain the efiect aimed at by the invention it is desirable to so form and adjust the knife cutting the brush jet that both of the jet portions separated by the knife remain in contact with the same during the entire period of cutting.

It is thus a condition that the knife must be adjusted into an inclined position relative to the axis of the jet in such a manner that the direction of the relative velocity Vr of the jet particles falls within the contour of the crosssection of the knife,.as will appear from the velocity diagram shown in Figure 6, wherein V and Vw represents the absolute velocity of the jet particles and of the knife W respectively.

In the commutator constructed according to the present invention at each brush place more jets. connected in parallel may naturally be used. Also the jets may be cut at each space between segments by two or more knives instead of by one knife only.

Having thus fully described my invention I claim as new and desire to secure by Letters Patent:

1. An electric commutating or switching device, comprising a plurality of movable segments, means for producing at least one conductive liquid jet co-acting with said segments and serving as a brush, and a knife of conductive material following the movement of the segments and insulated from the latter, said knife being so arranged as to cut said liquid jet substantially in the moment when it short-circuits two consecutive segments.

2. The electric commutating or switching device of claim 1, in which said knife is adjustable.

3. A rotating electric commutator, comprising a circumferential series of rotating spaced segments, means for producing conductive liquid jets serving as commutator brushes and co-acting with said segments,v and a conductive cutting device arranged in the neighbourhood of the space betweeneach pair of consecutive segments, said cutting device rotating together with the segments and being arranged to cut the said liquid jets in such a manner that the commute.- tion arcs are formed mainly between liquid surfaces only.

4. The rotating electric commutator of claim 3, in which said cutting device is adjusted circumferentially.

5. An electric commutator or the like comprising a plurality of movable segments, means for producing conductive liquid jets co-acting with said segments, adjacent ends of consecutive segments being mutually displaced in the direction of movement of the jet particles, and a knife of conductive material following the movement of said segments and arranged substantially in the space thus formed between such adjacent ends of consecutive segments, which knife serves to cut the liquid jets.

6. An electric commutator or the like, comprising a plurality of movable segments, stationary brushing devices co-acting with said segments and consisting each of means for producing two electrically interconnected conductive liquid jets which are mutually displaced both in the direction of movement of the seg- 'ments and in a direction perpendicular thereto, 

